I am really confused!!
Gram-positive or Gram-negative bacteria, which one has a higher surface negative charge? why?
Hello
In Gram positive bacteria the reason of this negative charge is the presence of teichoic acids linked to either the peptidoglycan or to the underlying plasma membrane. The charge in the bacterial cell wall is due to the electron release due to the catalytic activity during cell respiration. The Gram negative bacteria have an outer covering of phospholipids and Lipopolysaccharides. The lipopolysaccharides impart a strongly negative charge to surface of Gram negative bacterial cells.
Good luck.
The cell wall in bacteria contains lots of phosphate linings which helps in transportation of peptidoglycan from the vicinity of the cell to the external part. However, the cell wall in Gram positive bacteria contains teichoic acid, which confer greater negatively charged electrons. While, in Gram negative bacteria, the cell wall is made up of phospholipid and polysaccharides, that confer negatively charged net electrons to the cell surface. The layers of peptidoglycan is more dense in Gram positive bacteria than in Gram negative bacteria, as such, Gram positive bacteria has higher cell surface net negatively charged electrons than its counterpart.
Gram negative bacteria I think because it has more lipid and less piptedoglycan
Escherichia coli (Gram-negative) has more negatively charged surface than Staphylococcus aureus (Gram-positive), as determined by electrophoretic mobility measurements:
Article Difference in surface properties between Escherichia coli an...
Dear Sadegh Khorrami ,
This seemingly easy to answer question is rather complicated.
Gram-positive and gram-negative bacteria have differences in their membrane structure but it is clear that most of them have a negative charge.
The gram-negative bacteria have a layer of lipopolysaccharide at the external surface followed by a thin layer of peptidoglycan while the cell wall in gram-positive bacteria is mainly composed of a thick layer of peptidoglycan.
It has been shown, using zilver nanoparticles (AgNP), that the AgNPs were more active against gram-negative bacteria and since the electrostatic attraction between positively charged nanoparticles and negatively charged bacterial cells is shown to be an important aspect with regard to the antimicrobial activity of the AgNPs this suggests that Gram-negative bacteria have the highest negatively charged cell wall.
However the MIC against E. coli was found to be the lowest determined concentration among bacterial strains for positively charged AgNPs and therefor seem to suggest that the actual negatively charge vary a lot and depend on the characteristics of the bacterial species.
See for details on all this:
Abbaszadegan, A., Ghahramani, Y., Gholami, A., Hemmateenejad, B., Dorostkar, S., Nabavizadeh, M., & Sharghi, H. (2015). The effect of charge at the surface of silver nanoparticles on antimicrobial activity against gram-positive and gram-negative bacteria: a preliminary study. Journal of Nanomaterials, 16(1), 53.
https://www.hindawi.com/journals/jnm/2015/720654/
There is another reason why this question is not easy to answer, and I quote:
“As surface charge and surface potential both vary on a charge-regulated surface, accurate modeling of bacterial interactions with surfaces ultimately requires use of an electrostatic model that accounts for the charge-regulated nature of the cell surface.”
See for details:
Hong, Y., & Brown, D. G. (2008). Electrostatic behavior of the charge-regulated bacterial cell surface. Langmuir, 24(9), 5003-5009.
My Dears,
Thank you for all your answers, I appreciate your assistance.
It seems this issue is controversial, some of the answers are opposite each other. As far as I am concerned, gram-negative bacteria have a high negative surface charge. This article also confirms the expression; Chung YC et al / Acta Pharmacol Sin 2004 Jul; 25 (7): 932-936.
However, as Rob Keller argues, a few articles report the opposite results.
Gram-positive and gram-negative bacteria have differences in their membrane structure but it is clear that most of them have a negative charge.